1. Field
Embodiments of the invention generally relate to semiconductor and other electronic device processing, and more particularly, to an improved method for depositing a material on a substrate during a vapor deposition process.
2. Description of the Related Art
The electronic device industry and the semiconductor industry continue to strive for larger production yields while increasing the uniformity of layers deposited on substrates having increasingly larger surface areas. These same factors in combination with new materials also provide higher integration of circuits per unit area on the substrate. The need for greater deposition rate and process control regarding layer characteristics rises as the desire for an increased circuit integration.
Tantalum-containing layers, such as tantalum, tantalum nitride, and tantalum silicon nitride, are often used in multi-level integrated circuits and pose many challenges to process control, particularly with respect to contact formation. Barrier layers formed from sputtered tantalum or reactive sputtered tantalum nitride have demonstrated properties suitable for use to control copper diffusion. Exemplary properties include high conductivity, high thermal stability, and resistance to diffusion of foreign atoms.
Both physical vapor deposition (PVD) and atomic layer deposition (ALD) processes are used to deposit tantalum-containing layers in features of small size (e.g., about 90 nm wide) and high aspect ratios of about 5:1. However, it is believed that PVD processes may have reached a limit at this size and aspect ratio, while ALD processes suffer other problems. Common problems encountered during ALD processes include the lack of stability for the deposition rate and minimum control for the thickness of each deposited layer.
An ALD process generally contains a multiplicity of cycles, such that a substrate surface is sequentially exposed to two or more reagents or precursors during each ALD cycle while forming the deposited layer. The thickness of a deposited material is the product of the number of conducted ALD cycles by the thickness of each deposited layer. The deposition rate may be used to adjust the thickness of the deposited material. The deposition rate of each ALD cycle is usually controlled by the chemical nature of the particular process. Therefore, the deposition rate may be adjusted by controlling certain process conditions, such as the delivery rate of the gaseous reagent or precursor, modifying the exposure time during the ALD cycle, or adjusting the temperature of the process or precursor. However, the deposited material is usually non-uniformly formed on the substrate surface while adjusting the deposition rate by varying these process conditions.
Therefore, there is a need for increasing the stability of the deposition rate of a deposited layer while controlling the layer thickness during a vapor deposition process.